Embodiments of the present invention relate generally to new and useful improvements in ammunition cartridge assembly, and more particularly to ballistic sealing, component retention, and projectile launch control for an ammunition cartridge assembly. The present invention may also relate to a cased telescoped ammunition cartridge assembly.
Cased telescoped ammunition has been used successfully in small, medium, and large caliber applications. See, for example, U.S. Pat. Nos. 4,738,202 and 4,770,098, which disclose telescoped ammunition rounds utilizing nonstrategic materials. Small caliber is generally defined as less than 0.50 caliber, medium caliber is generally defined as between 0.50 caliber and 60 millimeters, and large caliber is generally defined as 60 millimeters and larger.
However, maintaining an effective seal remains an issue in all applications of cased telescoped ammunition. Generally, in conventional cartridge arrangements, component sealing is provided via press fits at the primer/case interface and the projectile/case interface. Such sealing under ballistic pressure at the case mouth is accomplished via expansion of the case against the chamber wall. The interfaces of a cased telescoped cartridge arrangement using a polymer case are substantially different in geometry and material characteristics, thus, rendering the conventional press fit sealing approaches ineffective.
Likewise, in a conventional cartridge assembly, component retention is provided via a press fits at the primer/case interface and the projectile/case interface. However, press fits are unsuitable for cased telescoped ammunition because the lightweight polymer materials used in cased telescoped ammunition will deform and degrade over the cartridge lifetime, as a result of residual stresses introduced by the press fits.
Furthermore, in conventional cartridge arrangements, the projectile protrudes from the case. The alignment of the protruding projectile is generally controlled via a case mouth and crimp arrangement. Since minimal projectile translation occurs before the projectile enters the barrel, shot start force is determined by the case crimp and barrel forcing cone profile. Neither of these approaches are applicable to a telescoped cartridge, since the projectile is initially seated within the cartridge.
In short, there exists a need in the art for a cased telescoped ammunition cartridge assembly that includes improved ballistic sealing, component retention, and projectile launch control.